This project focuses on investigating the response of fat cells, or adipocytes, to insulin. Upon ingestion of a meal, the pancreas secretes insulin, prompting adipose and muscle cells to accumulate glucose from the blood, in order to store energy for future use and to lower post-prandial blood glucose levels. Decreased responsiveness of adipose and muscle to insulin leads to the development of Type 2 diabetes, though the precise molecular defects that create this state are unknown. The process of glucose transport into the cell requires the activity of specific glucose transporters; in adipocytes and muscle cells, the primary transporter is the glucose transporter 4 (GLUT4). In the absence of insulin, GLUT4 is retained inside the cell, but upon stimulation of adipocytes by insulin, GLUT4 is trafficked to the cell surface. The increase in GLUT4 on the cell surface leads to increased transport of glucose into the cell. The experiments proposed in this application will examine the role of one particular protein, the small GTPase RAB10, in the process of insulin-regulated GLUT4 trafficking. First, a screen for proteins that interact with RAB10 will be conducted and analyzed in order to identify as-yet unknown factors involved in insulin-regulated GLUT4 trafficking. Second, a mouse with a conditional allele of Rab10 will be generated and the metabolic phenotype of these animals assessed. These experiments will test in vivo the current model of GLUT4 translocation that has been developed based on in vitro studies, an important step in translating basic research into clinical therapies. The studies proposed here will identify new candidates for therapeutic targets for the treatment of Type 2 diabetes, as well as advance our understanding of the fundamental biological processes underlying the response of adipocytes to insulin. These findings will undoubtedly be of great import to the scientific and clinical communities.